It is well known that phyllosilicates, such as smectite clays, e.g., sodium montmorillonite and calcium montmorillonite, can be treated with organic molecules, such as organic ammonium ions, to intercalate the organic molecules between adjacent, planar silicate layers, for bonding the organic molecules with a polymer, for intercalation of the polymer between the layers, thereby substantially increasing the interlayer (interlaminar) spacing between the adjacent silicate layers. The thus-treated, intercalated phyllosilicates, having interlayer spacings increased by at least 3 .ANG., preferably at least 5 .ANG., e.g., to an interlayer (interlaminar) spacing of at least about 10-25 .ANG. and up to about 100 Angstroms, then can be exfoliated, e.g., the silicate layers are separated, e.g., mechanically, by high shear mixing. The individual silicate layers, when admixed with a matrix polymer, before, after or during the polymerization of the matrix polymer, e.g., a polyamide--see U.S. Pat. Nos. 4,739,007; 4,810,734; and 5,385,776--have been found to substantially improve one or more properties of the polymer, such as mechanical strength and/or high temperature characteristics.
Exemplary prior art composites, also called "nanocomposites", are disclosed in published PCT disclosure of Allied Signal, Inc. WO 93/04118 and U.S. Pat. No. 5,385,776, disclosing the admixture of individual platelet particles derived from intercalated layered silicate materials, with a polymer to form a polymer matrix having one or more properties of the matrix polymer improved by the addition of the exfoliated intercalate. As disclosed in WO 93/04118, the intercalate is formed (the interlayer spacing between adjacent silicate platelets is increased) by adsorption of a silane coupling agent or an onium cation, such as a quaternary ammonium compound, having a reactive group which is compatible with the matrix polymer. Such quaternary ammonium cations are well known to convert a highly hydrophilic clay, such as sodium or calcium montmorillonite, into an organophilic clay capable of sorbing organic molecules.
In accordance with one embodiment of the present invention, intercalates are prepared by contacting a phyllosilicate with a monomeric onium ion spacing/coupling agent compound. To achieve the full advantage of the present invention, the onium ion should include at least one long chain radical (C.sub.6 +) that may be aliphatic, straight or branched chain, or aralkyl. Exemplary of such suitable C.sub.6 + onium ion molecules include primary, secondary, tertiary or quaternary ammonium ions, sulfonium ions, phosphonium ions, oxonium ions, or any ion of an element in Groups V or VI of the periodic table of elements.
In accordance with an important feature of the present invention, best results are achieved by mixing the layered material with the onium ions, e.g., C.sub.6 + onium ion spacing/coupling agent, in a concentration of at least about 2% by weight, preferably at least about 5% by weight onium ion compound, more preferably at least about 10% by weight onium ion compound, and most preferably about 30% to about 80% by weight, based on the weight of onium ion compound and carrier (e.g., water, with or without an organic solvent for the onium ion compound) to achieve better sorption of the onium ion spacing/coupling agent compound between the platelets of the layered material. Regardless of the concentration of onium ion compound in the intercalating composition, the weight ratio of MXD6 nylon intercalant:layered material should be at least 1:20, preferably at least 1:10, more preferably at least 1:5, and most preferably about 1:4 to achieve sufficient MXD6 nylon (or its monomeric reactants) intercalation between adjacent inner surfaces of adjacent platelets of the layered material. The onium ion spacing/coupling agent compound sorbed between and bonded to (or complexed with) the silicate platelets via ion-exchange causes surprisingly easy intercalation of the MXD6 nylon polymer, or its monomeric reactants for MXD6 nylon (meta-xylylene diamine and adipic acid) polymerization in-situ.
In accordance with an important feature of the present invention, it has been found that an onium ion-intercalated phyllosilicate, such as a smectite clay, can be intercalated easily with MXD6 nylon to form an onium ion/MXD6 nylon co-intercalate that has excellent intercalate dispersibility in a matrix polymer, particularly an MXD6 nylon matrix polymer and has unexpectedly low gas (particularly O.sub.2) permeability in an MXD6 nylon matrix polymer. The intercalate also can be added to any other matrix polymer to enhance a number of properties of the matrix polymer, including tensile strength, heat distortion temperature, gas-impermeability, elongation, and the like.
The onium ion/MXD6 nylon co-intercalates and/or exfoliates thereof can be admixed with a polymer or other organic monomer compound(s) or composition to increase the viscosity of the organic compound or provide a matrix polymer/intercalate and/or matrix polymer/exfoliate composition to enhance one or more properties of the matrix polymer, particularly an MXD6 nylon matrix polymer.
The onium ion M6 nylon co-intercalating process of the present invention provides an intercalate that can be added, particularly by direct compounding (mixing the intercalate directly into a matrix polymer melt) of the intercalate with any matrix polymer, e.g., all market available resin systems, particularly epoxy resins such as: Bisphenol A-derived resins, Epoxy cresol Novolac resins, Epoxy phenol Novolac resins, Bisphenol F resins, polynuclear phenol-glycidyl ether-derived resins, cycloaliphatic epoxy resins, aromatic and heterocyclic glycidyl amine resins, tetraglycidylmethylenedianiline-derived resins, nylons, such as nylon-6 and nylon 66, and particularly MXD6 nylon.